The present invention relates to a drop discharge device for discharging liquid raw material or fuel for processing or actuating the fluid thereby, the device being assembled to a raw material/fuel discharge device of various apparatuses.
A conventional drop discharge device typically includes a pressurizing means for achieving discharge of liquid, a pressurizing chamber for achieving discharge of liquid to be discharged, a liquid discharge nozzle connected to the pressurizing chamber, and an introducing hole for supplying liquid to the pressurizing chamber. Usually, a plurality of such devices are assembled to a driving means for a raw material/fuel discharge device as units for discharging minute liquid-drops. The liquid introducing holes of the plurality of adjoining drop discharge devices are connected to a common liquid supply path, and piezoelectric/electrostrictive elements are provided on a part of wall portions of the liquid pressuring chambers. To actuate the driving means for the raw material fuel discharge device, wall portions of the liquid pressurizing chambers are deformed by applying specified voltage signals to the piezoelectric/electrostrictive elements, and through pressure generated in the liquid pressurizing chambers, liquid supplied to the liquid pressuring chambers are sprayed out from the nozzles.
When liquid was to be discharged in large amounts for some applications of a raw material/fuel discharge device, the number of nozzles of the plurality of drop discharge devices to be mounted was increased, and time intervals for applying the specified voltage signals to the piezoelectric/ electrostrictive elements were decreased to thereby improve voltage application per unit time to decrease discharge cycles, or the voltage was increased.
However, when liquid is to be discharged in large amounts and further in a successive manner as in the above-described case, that is, when a plurality of nozzles which perform discharge at a flow rate of not less than several tens of pL per one discharge of a single nozzle, at a discharge cycle of not less than several kHz, and for not less than several tens of ms, are provided at distances of several hundreds of xcexcm, liquid-drops will remain in the nozzles or on the peripheries thereof and result in unstable discharge or a phenomena in which discharged drops are absorbed by liquid-drops on the nozzle peripheries to make spraying impossible.
Thus, the inventors of the present invention have devised a drop discharge device comprising a pressurizing means for achieving discharge of liquid, a pressurizing chamber for pressurizing the liquid to be discharged, a liquid discharge nozzle connected to the liquid pressurizing chamber, and a layer treated for repelling the liquid disposed around the discharge hole of the nozzle, wherein the layer for repelling liquid includes portions of different liquid-repelling properties spaced from each other. With this arrangement, liquid- drops that have been discharged from the nozzle, but remain as large liquid-drops on the layer treated for repelling liquid without being scattered, will be eliminated at portions of different liquid-repelling properties, and discharge deficiencies caused through liquid-drop residues at the nozzle discharge outlet will be prevented.
The layer treated for repelling liquid comprised by arranging portions of different liquid-repelling properties spaced from each other includes, in addition to a first liquid- repelling layer disposed in a periphery of the discharge hole of the nozzle, at least a second liquid-repelling layer connected to an outer edge of the first liquid-repelling layer, wherein liquid-repelling properties of the second liquid-repelling layer of different liquid-repelling properties may be either superior or inferior than those of the first liquid-repelling layer.
According to another embodiment of the present invention, portions with inferior liquid-repelling properties from among the portions of different liquid-repelling properties of the layer for repelling liquid may be formed by gaps in the layer for repelling liquid at the stage of designing or by thinning the layer thickness or partially omitting the layer for repelling liquid by performing cutting, dissolving or decomposing after forming.
An invention according to another embodiment relates to a drop discharge device with portions with inferior liquid-repelling properties from among the portions of different liquid-repelling properties of the layer are formed by cutting, dissolving or decomposing the layer for repelling liquid to assume concave sections. An invention according to another embodiment relates to a drop discharge device with portions of different liquid- repelling properties of the layer are formed of a layer treated for repelling liquid made of a material with different liquid-repelling properties.
An invention according to another embodiment relates to a drop discharge device wherein distances L from boundaries of portions of different liquid-repelling properties of the layer treated for repelling liquid to an outer periphery of the discharge hole of the nozzle are identical to each other. With this arrangement, liquid-drops will contact boundaries of portions of different liquid-repelling properties regardless of an expanding direction of the liquid-drops so that liquid may be reliably omitted.
The distance L from boundaries of portions of different liquid-repelling properties of the layer treated for repelling liquid to the outer periphery of the discharge hole of the nozzle is preferably in a range of 200 to 500 xcexcm. In case the distance L is not less than 200 xcexcm, exact positioning to the outer edge of the discharge hole of the nozzle is enabled, a layer thickness thereof made large to be hard to peel off, and a liquid-repelling layer of high durability can be obtained. Since the distance L is not more than 500 xcexcm, which is a maximum diameter of a general liquid-drop causing unstable discharge of the nozzle, liquid-drops in larger conditions will contact portions of different liquid-repelling properties to be eliminated, and it is accordingly possible to prevent discharge deficiencies owing to liquid-drops remaining in the nozzle discharge outlet.
Another embodiment of the present invention relates to a drop discharge device wherein distances L from boundaries of portions of different liquid-repelling properties of the layer treated for repelling liquid to an outer periphery of the discharge hole of the nozzle satisfy d greater than L greater than 0.1 d with respect to a maximum liquid-drop diameter d of a discharged liquid-drop formed on the layer treated for repelling liquid.
Here, the maximum liquid-drop diameter d of discharged liquid formed on the layer treated for repelling liquid is a liquid-drop diameter obtained in a measuring device with a surface on which the nozzle is formed being provided in a vertical manner and a discharge direction of liquid-drops set in a horizontal manner, when a liquid-drop formed on the liquid-repelling surface is deformed from its drop-like shape or is dropped downward.
Another embodiment of the present invention relates to a drop discharge device wherein a plurality of nozzles are provided with a pressurizing chamber with distances M between outer peripheries of discharge holes of adjoining nozzles which satisfy d less than M with respect to a maximum liquid-drop diameter d of a discharged liquid-drop formed on the layer treated for repelling liquid.
According to another embodiment of the present invention wherein liquid- repelling properties of a second liquid-repelling layer of different liquid-repelling properties are inferior than those of the first liquid-repelling layer, the drop discharge device in any one of the above embodiments is arranged in that a porous liquid absorbing layer is disposed on a periphery of the layer treated for repelling liquid. With this arrangement, even if liquid-drop remaining in the nozzle discharge outlet to cause discharge deficiencies shall become large, this liquid-drop will be penetrated upon contacting the liquid absorbing layer so that the liquid-drop that has become larger will be reduced to a size similar to those at peripheries of the discharge hole of the nozzle.
An invention according to another embodiment of the present invention provides a drop discharge device according to any one of the above embodiments, wherein the nozzle(s) and pressurizing chamber are made of zirconia ceramics. With this arrangement, wettability of flow paths within the nozzle and the pressuring chamber with fluid will be improved such that air bubbles hardly remain or intermingle, and discharge may be stabilized.